Objective To explore the effect of tri pterygium glycoside (TG) on the skeletal muscle atrophy and apoptosis after nerve allograft. Methods Twenty Wistar male rats were adopted as donors, weighing 200-250 g, and the sciatic nerves were harvested. Fifty SD male rats were adopted as recipients, weighing 200-250 g. Fifty SD rats were made the models of10 mm right sciatic nerve defect randomly divided into five groups (n=10): group A, group B, group C, group D and group E.groups A and B received fresh nerve allograft, groups C and D received sciatic nerve allograft pretreated with TG, and group E received autograft. The SD rats were given medicine for 5 weeks from the second day after the transplantation: groups A and E were given physiological sal ine, groups B and D TG 5 mg/ (kg·d), and group C TG 2.5 mg/ (kg·d). At 3 and 6 weeks, respectively, after nerve transplantation, general observation was performed; the structure of skeletal muscles was observed by HE staining; the diameter of skeletal muscles was analyzed with Image-Pro Plus v5.2; the ultrastructure of skeletal muscles was observed by TEM; the expressions of Bax and Bcl-2 were detected by immunohistochemical staining; and the apoptosis of skeletal muscles was detected by TUNEL. Results All rats survived to the end of the experiment. In general observation, the skeletal muscles of SD rates atrophied to different degrees 3 weeks after operation. The muscular atrophy in group A was more serious at 6 weeks, and that in the other groups improved. The wet weight, fiber diameter and expression of Bcl-2 in group A were significantly lower than those in groups B, C, D and E (P lt; 0.01)；those in groups B, C and D were lower than those in group E (P lt; 0.05); and there were no significant differences among groups B, C and D (P gt; 0.05). The apoptosis index and expression of Bax in group A were significantly higher than those in groups B, C, D and E (P lt; 0.01)；those in groups B, C and D were higher than in groupE (Plt; 0.05); and there were no significant differences among groups B, C and D (P gt; 0.05). Three weeks after nerve allograft, under the l ight microscope, the muscle fibers became thin; under the TEM, the sarcoplasmic reticulum was expanded. Six weeks after nerve allograft, under the l ight microscope, the gap of the muscle fibers in group A was found to broaden and connective tissue hyperplasia occurred obviously; under the TEM, sarcomere damage, serious silk dissolution and fragmentary Z l ines were seen in group A, but the myofibrils were arranged tidily in the other groups, and the l ight band, dark band and sarcomere were clear. Conclusion TG can decrease the skeletal muscle atrophy and apoptosis after nerve allograft. The donor’s nerve that is pretreated with TG can reduce the dosage of immunosuppressant for the recipient after allograft.